Lost-motion-compensating means for gear-hobbing machines



J. K. SCHOFIELD LOST MOTION COMPENSATING MEANS FOR GEAR HOBBING MACHINESFiled Oct. 14 1922 2 3 x a 7 3 5 1 0 v 0 3 2 u m 2 1 w l 1 H 2 u w M .u3 2 H z 2 E" u W "um" m u 5 2 w INVENTGR Patented Nov. 18, 1924.

UNITED sr TES PATENT OFFICE.

JOSEPH K. SCHOI'IEILD, OF HARTFORD, CONNECTICUT, ASSIGNOR TO BEAT! 80WHIT- NEY, CO'MPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW LOST-MOTION-COMPENSATING MEANS FOR GEAR-HQBBING MACHINES.

Application filed October 14, 1922. Serial No. 594,566.

To all whom it may concern:

Be it known that I, .losnrn K. Sonormm, a citizen of the United States,residing at Hartford, in the county of Hartford and State ofConnecticut, have invented certain new and useful Improvements in'.Lost- Motion-Compensating Means for Gear-Hobbing Machines, of which thefollowing is a specification.

This invention relates generally to gear hobbing machines and inparticular to mechanism adapted to be applied to machines of this typewhereby all lost motion or back lash between the members of the drivingconnections extending from the hob spindle to the work carrying spindleis entirely eliminated.

It is an object of the invention to provide a simple and inexpensivemechanism which will eliminate all inaccuracies in the hobbing operationdue to lost motion or back lash between parts of the machine and providea mechanism for this purpose which will not place a drag upon the workspindle.

One feature which enables me to accomplish the above named object isthat I provide two driving connections from the hob spindle to the worksupporting and rotating spindle, both of these connections comprisingpositive gear connections. One of these gear connections extendsdirectly to the indexing mechanism on the work spindle while the otherconnection rotates one end of a torsional spring. The opposite end ofthe torsional spring is connected to a pinion also in mesh with theindexing mechanism. By these means timing of the work spindle iscontrolled entirely by the positive gear connections and the second gearconnection, that is, the one including the torsional spring, tends bythe resilienc of the torsional spring to force the wor spindle as faradvanced as possible. In this way, all of the lost motion or back lashof the parts in the positive driving connection is constantly held onthe same side of the gear teeth. All possibility of lost motion in thisgear connection causing inaccuracies in the work is eliminated.

More particularly, it is an object of the present Invention to providesubstitute means for the form of lost motion compensating means:described and claimed in the copending applications filed by E.Buckingions, preferably elongated,

the cooperative mechanism of a gear-hobhing machine provided with thepresent invention. It will be understood, however, that the inventioncan be otherwise embodied and that the drawing is not to be construed asdefining or limiting the scope of the invention, the claims appended tothis specification being relied upon for that purpose. I

In the drawing:

Figure 1 is a diagrammatic plan view of the mechanism forming thepresent invention, and

Fig. 2 is a front elevation of the mechanism also showndiagrammatically.

In the above mentioned drawing, I have shown but one modification of theinvention which is now deemed preferable but it is to be understood thatchanges and modifications maybe made within the scope of the appendedclaims without departing from the spirit of the invention.

Briefly, my invention in its broadest as- I pect comprises the followingprincipal parts: first, a hob supporting and rotating spindle preferablyprovided with suitable driving means d1rectly in alignment therewith;second, a work spindle adapted to rotate the work in timed relation tothe rotation of the hob spindle and adapted simultaneously to advancethe work axially past the hobthird, a geared driving connectionextending from the hob spindle directly to the work supporting androtating spindle; fourth, another set of gearing between the hob spindleand the work spindle which includes a torsional spring therein, thetension of which may be adjusted and fifth, pinforming the final drivingelements of both gear connections and adapted to directly engage theindexing gearfastened directly to and moving axially I withv the workspindle.

Referring more in detail to the figures may be rotated andsimultaneously advanced axially. In the preferred embodiment of theinvention the axes of the hob and also the work spindle are fixed. inpredetermined angular relation. ()n this spindle 14 I provide anindexing gear 15 directly attached thereto. By any suitable fasteningmeans, I mount gear blanks W which are adapted to have teeth out thereinby the hob 11, these gears W being mounted coaxially with the workspindle 14 in the usual way. In alignment with the work spindle 14 is ascrew 16 engaging a threaded member 17 attached to or forming a part ofthe base of the machine. It will be seen from this construction that asthe work spindle 14 is rotated, it will be simultaneously advanced in anaxial direction by engagement of the screw 16 within the nut 17.

In order to rotate the work spindle 14 in timed relation to the rotationof the hob spindle 10 during the bobbing operation, I

, provide a-positive geared driving connection between these twospindles. Preferably, a bevel gear 20 fixed to the hob spindle 10 is inmesh with another bevel gear 21 on a short intermediate shaft having apinion or gear 22. In mesh with the gear 22 is an idler gear 23 which inturn engages with another gear 24. Preferably, gears 22 and 24 arearranged so that they may be conveniently removed and the idler '23adjust. ably positioned so that it may be placed in 1 engagement withboth of them. The

24 1s fixed to and drlves a shaft 25 having an elon ted pinion 26thereon. This pinion 26 is a apted to engage directly with the teeth ofthe indexing gear 15 in all axial positions of the work spindle 14 andgear 15 during operation.

A second drivin connection is provided between the hob spmdle 10 andwork spindle 14 which 8.1801113} be driven from the bevel ear 20directly mounted upon the hob spinle 10. This connection comprises abe'vel gear 30 ona shaft having a gear 31 thereon which is in mesh withan intermediate gear 32; The gear 32 is 'in mesh with anotherintermediate gear 33 which engages a gear 34. The ratio of gears 31 and34 is identical with the ratio of gears 22 and 24 respectively so thatthe gear 34 isrotated at exactly the same speed as the gear 24 and, asthere are two intermediate gears between the gears 31 and 34 instead ofbut one as between the gears 22 and 24, the gear 34 rotates in theopposite direction as compared with gear 24. The gear 34 is mounted on asleeve 35 which is provided with a small housing 36 enclosing a wormwheel 37 having a worm 38 in engagement therewith. The worm 38 ismounted upon'a short transverse shaft 39 rotatably mounted in bearingsprovided in the housing 36. Knurled heads 40 on ppposite ends of thisworm shaft 39 provide means for rotating the worm 38 and the worm wheel37 therewith. The worm wheel 37 is mounted upon an inner sleeve 41coaxial with and extending through the first sleeve 35 and at one end ofthis sleeve 41, the end of a torsional spring 42 is permanently secured.A pinion 43, preferably in the form of a sleeve is mounted so as toengage the indexing wheel .15 above mentioned; and, at one end .of thispinion gear 43, the opposite end of the torsional spring 42 ispermanently secured. In order to keep the sleeves 35 and 41 in alignmentwith each other and with the pinion 43, I preferably:

provide a shaft 44 extending through the sleeve 41 and the pinion 43. Itwill be seen from theabove description therefore that rotation of thegear 34 will rotate the sec- 0nd pinion 43 and, as the ratio betweengears 31 and 34 is the same as between gears 22 and 24, the secondpinion 43 is driven at exactly the same speed as the first pinion 26.

The above described means comprising the sleeve 35, the housing 36 andcontained parts constitute means for varyin the torsion applied to thespring 42. If esired, however,

these parts may be omitted and the torsion of the spring 42 may beapplied by slightly rotating one of the ears in the driving connectiontherefor while the other connections are held stationary. I

The purpose for which the torsional spring 42 is inserted in the drivingconnections for the second pinion 43 is to resihently force this pinion43 rotatably as far as possible in order to firmly hold the indexinggear 15 in advanced position. I accomplish this by providing an initialtorque between the gear 34 and pinion 43. This is accomplished byrotating the worm wheel 37 relative to'its housing 36. By relativerotation of the housing 36 and worm wheel 37,

any desired amount of torsion can be applied to this torsional spring42. In operation it will be understood that the housing 36 and wormwheel 37 within this housing rotate simultaneously without relativemovement so that the torsion of the spring 42 is not varied duringoperation except by variations in the back lash between the members ofthe driving connections 21' to 26.

It will be seen from the above described construction that the timedrelation between rotation of the hob spindle 10 and the work spindle 14'is governed. entirely by the first v The driving driving connectionsincluding the gears 20v to 26 and that this ratio may be varied withinwide limits by substitutmg gears of different numbers of teeth for thegears 22 and 24 shown. This change of ratio is, of course, necessary toaccommodate the machine for bobbing gears of different numbers of teeth.connection provided between gears 32 and 35 by reason of theinterposition of the torsional spring 42, tends to rotate the pinion 43and then the gear 15 as far as permitted by rotation of the pinion 26.The positive connections prevent the torsional spring 42 from unwindingand thus advancing the indexing wheel 15 beyond its proper position. Theindexing gear 15, however, is always held as far advanced as permittedby this positively-driven pinion and thus all lost motion or back lashbetween the members of the positive drivin train is continuously held onthe same si e of the teeth. In this way all lost motion or back lashbetween these members during operation does not in any way afiect theprecision of operation of the mechanism.

at I claim is:

1. A gear bobbing machine having co-' operating mechanism comprising, awork supporting and rotating spindle, a rotatable hob supporting meanscomprising a second spindle, a hob thereon, drivin means for said hobspindle and work spin le, two driving connections between said spindles,the ratio of said driving connections being the same, and means to forceone of said driving connections in advance of the other to eliminate theefiects of lost motion between members of the driving connections.

' the rati'o'of said 2. A gear hobbing machine having o0 operatingmechanism comprising, a work supporting and rotating spindle, a.rotatable hob supporting means comprising a secon spindle, a hobthereon, driving means for said hob spindle and work spindle, twodrivingconnections between said spindles, driving connections being thesame, and a torsional spring inserted in one of said connections.

3. A gear bobbing machine having cooperating mechanism comprising,- awork supporting and rotating spindle, a rotatable hob supportingmeanscomprising a second spindle, a hob thereon, driving means for said hobspindle and work spindle, two driving connections between said spindles,the ratio of said driving connections being the same, a torsional springinserted in one of said connections, and means to vary the forsion ofsaid spring.

4. A gear hobbing machine having cooperating mechanism comprising, awork supporting and rotating spindle, a rotatable hob supporting meanscomprising a second spindle, a hob thereon, driving means for said hobspindle and worle' spindle, two

' supporting means 'nections being positive geared driving connectionsbetween said spindles, the ratio of said driving connections being thesame, and a torsional spring inserted in one of said connections.

5. A gear bobbing machine having cooperating mechanism comprising, awork supporting and rotating spindle, a rotatable hob supporting meanscomprising a. second spindle, a hob thereon, driving means for said hobspindle and work spindle, two driving connections between said spindles,the ratio of said driving connections being the same, and resilientmeans inserted in one of said connections to advance one of the drivingconnections as far as permitted by the other connection.

6. A gear hobbing machine having cooperating mechanism comprising, awork supporting and rotating spindle, a rotatable hob for comprising asecond spindle, a hob thereon, driving means for said hob spindle andwork spindle, two driving connections between said spindles, the ratioof said driving connections being the same, and a. torsional springinserted in one of said connections to advance one of the drivingconnections as far as permitted by the other connection.

'2'. A gear hobbing machine having cooperating mechanism comprising, awork supporting and rotating spindle, a rotatable hob supporting meanscomprising a second spindle, a hob thereon, driving means for said hobdisposed in alignment therewith, and two driving connections from saidhob driving means to said Work spindle whereby said hob and spindle maybe rotated in timed relation to each other, one of said connectionsbeing positive throughout and the other adapted to be forced in advanceof the other to eliminate the effects of lost motion d between membersof the driving connections.

8. A gear bobbing machine having cooperating mechanism comprising, aWork supporting and rotating spindle, a rotatable hob supporting meanscomprising a second spindle, a hob thereon, driving means for said hobdisposed in alignment therewith, and two driving connections from saidhob driving means to said work spindle whereby said hob and spindle maybe rotated in timed relation toveach other, one of said conthroughoutand the other including a resilient element adapted to force saidspindle. as far advanced as permitted by said first connection.

9. A gear hobbing machine having cooperating mechanism comprising, awork supporting and rotating spindle, a rotatable hob supporting meanscomprising a second spindle, a hob thereon, driving means for said hobdisposed in alignment therewith, and two driving connections from saidhob driving means to said work spindle whereby said hob and spindle maybe rotated in timed relation to each other, one of said connectionsbeing positive throughout, and the erating mechanism comprising, a worksupporting and rotating spindle, a rotatable hob supporting meanscomprising a second spindle, a hob thereon, driving means for said hobdisposed in alignment therewith,

and two driving connections from said hob driving means 'to said workspindle whereby said hob and spindle may be rotated in timed relation toeach other, one of said connections being positive throughout and theother including a torsional spring adapted to force said spindle as faradvanced as permitted by said first connection, and worm and worm wheelmechanism to vary the torsion of said spring.

In testimony whereof, I hereto afiix my signature.

JOSEPH K. SCHOFIELD.

